解决自定义leftBarButtonItem返回手势失效的方法

考虑到interactivePopGestureRecognizer也有delegate属性，替换默认的self.navigationController.interactivePopGestureRecognizer.delegate来配置右滑返回的表现也是可行的。在主ViewController中：

- (void)viewDidLoad {　　[super viewDidLoad];　　self.navigationController.interactivePopGestureRecognizer.delegate = self;// 重新指定代理}

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if (self.navigationController.viewControllers.count == 1) { // 关闭主界面的右滑返回
        return NO;
    } else {
        return YES;
    }
}